Tennyo Masaki is Tenchi's sister and looks almost identical to their mother, Kiyone—so much so that the two used to swap places to mess with Tenchi when he was younger. Her father is listed as Nobuyuki Masaki, though there's some ambiguity about whether he's actually her biological dad, especially since it's never clarified in the OVA whether Nobuyuki is even fully human or part Jurian.
Despite her youthful appearance, Tennyo is well into her 80s. The series doesn't really explain how she's managed to age so slowly, which fans often chalk up to potential Jurian heritage or whatever other cosmic shenanigans run in her family.
Content compiled by AnimeList.moe from publicly available sources.
